MEMS gyroscope with frequency regulation and electrostatic cancellation of the quadrature error
First Claim
1. A MEMS gyroscope, comprising:
- a supporting structure;
a mobile mass mobile with respect to the supporting structure in a driving direction and in a sensing direction, the driving direction and the sensing direction being perpendicular to each other, the mobile mass being affected by a quadrature error caused by a quadrature moment;
a driving structure coupled to the mobile mass and configured to control movement of the mobile mass in the driving direction at a driving frequency, the mobile mass having a variable resonance frequency that differs from the driving frequency by a frequency mismatch;
motion-sensing electrodes coupled to the mobile mass and configured to detect movement of the mobile mass in the sensing direction; and
quadrature-compensation electrodes coupled to the mobile mass and configured to generate a compensation moment opposite to the quadrature moment; and
a compensation controller configured to bias the quadrature-compensation electrodes with at least one compensation voltage that drives the mobile mass at a preset frequency mismatch, wherein the quadrature-compensation electrodes comprise a first quadrature-compensation electrode and a second quadrature-compensation electrode, and the compensation controller is configured to bias the first and second quadrature-compensation electrodes at first and second compensation voltages V1, V2, respectively, where V1 and V2 are chosen for satisfying the equation;
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Abstract
A MEMS gyroscope, wherein a suspended mass is mobile with respect to a supporting structure. The mobile mass is affected by quadrature error caused by a quadrature moment; a driving structure is coupled to the suspended mass for controlling the movement of the mobile mass in a driving direction at a driving frequency. Motion-sensing electrodes, coupled to the mobile mass, detect the movement of the mobile mass in the sensing direction and quadrature-compensation electrodes are coupled to the mobile mass to generate a compensation moment opposite to the quadrature moment. The gyroscope is configured to bias the quadrature-compensation electrodes with a compensation voltage so that the difference between the resonance frequency of the mobile mass and the driving frequency has a preset frequency-mismatch value.
7 Citations
15 Claims
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1. A MEMS gyroscope, comprising:
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a supporting structure; a mobile mass mobile with respect to the supporting structure in a driving direction and in a sensing direction, the driving direction and the sensing direction being perpendicular to each other, the mobile mass being affected by a quadrature error caused by a quadrature moment; a driving structure coupled to the mobile mass and configured to control movement of the mobile mass in the driving direction at a driving frequency, the mobile mass having a variable resonance frequency that differs from the driving frequency by a frequency mismatch; motion-sensing electrodes coupled to the mobile mass and configured to detect movement of the mobile mass in the sensing direction; and quadrature-compensation electrodes coupled to the mobile mass and configured to generate a compensation moment opposite to the quadrature moment; and a compensation controller configured to bias the quadrature-compensation electrodes with at least one compensation voltage that drives the mobile mass at a preset frequency mismatch, wherein the quadrature-compensation electrodes comprise a first quadrature-compensation electrode and a second quadrature-compensation electrode, and the compensation controller is configured to bias the first and second quadrature-compensation electrodes at first and second compensation voltages V1, V2, respectively, where V1 and V2 are chosen for satisfying the equation; - View Dependent Claims (2, 3, 4)
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5. A control method for controlling a MEMS gyroscope, comprising:
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driving a mobile mass in a driving direction and at a driving frequency; detecting a movement of the mobile mass in a sensing direction, perpendicular to the driving direction, wherein the mobile mass is affected by quadrature error caused by a quadrature moment in the sensing direction and having a variable resonance frequency, the difference between the resonance frequency and the driving frequency forming a frequency mismatch; generating a compensation moment opposite to the quadrature moment via quadrature-compensation electrodes coupled to the mobile mass; and biasing the quadrature-compensation electrodes with at least one compensation voltage that drives the mobile mass with a preset frequency mismatch, wherein biasing the quadrature-compensation electrodes comprises applying a first compensation voltage V1 to a first quadrature-compensation electrode and applying a second compensation voltage V2 to a second quadrature-compensation electrode and V1 and V2 satisfy the equation; - View Dependent Claims (6, 7)
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8. A method for setting compensation parameters in a MEMS gyroscope, comprising:
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driving a mobile mass of the MEMS gyroscope in a driving direction and at a driving frequency; applying a plurality of pairs of values of compensation voltages V1, V2 to a first quadrature-compensation electrode and a second quadrature-compensation electrode coupled to the mobile mass and detecting a corresponding plurality of frequency mismatch values Δ
f0 between the driving frequency and a resonance frequency of the mobile mass;detecting, from the plurality of frequency mismatch values, which of the pairs of values of the compensation voltages V1, V2 are associated with a desired frequency mismatch value Δ
f0d;detecting, from the pairs of values of the compensation voltages, which pair of values makes Qel+Qγ
=0wherein; Qel is a compensation quadrature given by;
Qel=kQ[(VR−
V1)2−
(VR−
V2)2],Qγ
is quadrature error,VR is a biasing voltage of the mobile mass, and kq is a proportionality constant linking the compensation quadrature Qel to the compensation moment Mel; and storing the pair of values of the compensation voltages V1, V2 that makes Qel+Qγ
=0.- View Dependent Claims (9, 10, 11)
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10. The method of claim 8, further comprising:
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measuring a driving frequency fd of the mobile mass in a driving direction through a driving measurement structure coupled to the mobile mass; and measuring the sensing resonance frequency ω
S0 and measuring the parameter ks/J by applying appropriate values of the compensation voltages V1, V2.
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11. The method of claim 8, wherein applying a plurality of pairs of compensation voltage values V1, V2 and detecting a corresponding plurality of values of frequency mismatch Δ
- f0 comprises;
generating a table of frequency mismatch values Δ
f0.
- f0 comprises;
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12. An electronic system comprising:
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a MEMS gyroscope including; a supporting structure; a mobile mass mobile with respect to the supporting structure in a driving direction and in a sensing direction, the driving direction and the sensing direction being perpendicular to each other, the mobile mass being affected by a quadrature error caused by a quadrature moment; a driving structure coupled to the mobile mass and configured to control movement of the mobile mass in the driving direction at a driving frequency, the mobile mass having a variable resonance frequency that differs from the driving frequency by a frequency mismatch; motion-sensing electrodes coupled to the mobile mass and configured to detect movement of the mobile mass in the sensing direction; and quadrature-compensation electrodes coupled to the mobile mass and configured to generate a compensation moment opposite to the quadrature moment; and a control unit that includes a compensation controller configured to bias the quadrature-compensation electrodes with at least one compensation voltage that drives the mobile mass at a preset frequency mismatch, wherein the quadrature-compensation electrodes comprise a first quadrature-compensation electrode and a second quadrature-compensation electrode, and the compensation controller is configured to bias the first and second quadrature-compensation electrodes at first and second compensation voltages V1, V2, respectively, where V1 and V2 are chosen for satisfying the equation; - View Dependent Claims (13, 14, 15)
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Specification